dt-bindings: soc: qcom: Add devicetree binding for QCOM SPM

Add devicetree binding for Qualcomm Subsystem Power Manager (SPM).
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210729155609.608159-3-angelogioacchino.delregno@somainline.org

Documentation/devicetree/bindings/soc/qcom/qcom,spm.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/soc/qcom/qcom,spm.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Qualcomm Subsystem Power Manager binding
+
+maintainers:
+  - Andy Gross <agross@kernel.org>
+  - Bjorn Andersson <bjorn.andersson@linaro.org>
+
+description: |
+  This binding describes the Qualcomm Subsystem Power Manager, used to control
+  the peripheral logic surrounding the application cores in Qualcomm platforms.
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - qcom,msm8226-saw2-v2.1-cpu
+          - qcom,msm8974-saw2-v2.1-cpu
+          - qcom,apq8084-saw2-v2.1-cpu
+          - qcom,apq8064-saw2-v1.1-cpu
+      - const: qcom,saw2
+
+  reg:
+    description: Base address and size of the SPM register region
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+
+additionalProperties: false
+
+examples:
+  - |
+    cpus {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        cpu@0 {
+            compatible = "qcom,kryo";
+            device_type = "cpu";
+            enable-method = "qcom,kpss-acc-v2";
+            qcom,saw = <&saw0>;
+            reg = <0x0>;
+            operating-points-v2 = <&cpu_opp_table>;
+        };
+    };
+
+    saw0: power-manager@f9089000 {
+        compatible = "qcom,msm8974-saw2-v2.1-cpu", "qcom,saw2";
+        reg = <0xf9089000 0x1000>;
+    };
+
+...